Experimental study on the mechanism of CO2/external fluid interaction in shale pore structure

Abstract

At present, there is a lack of comparative studies between quantitative method and nuclear magnetic resonance method, and a systematic study on the mechanism of CO₂ under different types of shale pore structure conditions. In this paper, the quantitative method and nuclear magnetic resonance method are used to study the mechanism of CO₂/external fluid interaction in shale oil reservoirs, and the main parameter changes such as shale porosity after CO₂/external fluid interaction are analyzed. Then, X-ray diffractometer is used to conduct mineral and clay mineral composition testing of shale whole rock before and after the action of CO₂/external fluid, and the changes in microscale minerals of shale is analyzed. Results show that: (a) for laminated shale, supercritical CO₂ and CO₂ + slick water mainly improve the pore structure of microscale pores. (b) Supercritical CO₂ and supercritical CO₂ + slick water generally have an improvement effect on the pores of shale with well-developed bedding planes.(c) There was no significant change in shale mineral composition (<±2 %) after the separate action of supercritical CO₂ and slick water.